The following correction was printed in the Guardian's Corrections and clarifications column, Tuesday 7 July 2009

In the article below we said that a one-time footballer convicted of murder had been a "Brentford and Maidstone Town player". Brentford has said that Mario Celaire (aka Mario McNish) never played for the club; there is no Maidstone Town, but there is Maidstone United, his club.

A rapist who became the first person in UK history convicted of a crime for which he was previously found not guilty has been given two life sentences for killing a former girlfriend and trying to murder another.

Mario Celaire, a former footballer, had denied beating Cassandra McDermott, 19, and leaving her to die alone at her mother's house nearly eight years ago. He was acquitted of her murder after a trial in 2002.

Six years later, Celaire, 31, from Sydenham in south London, attacked another ex-girlfriend, Kara Hoyte, with a hammer.

The assault left Hoyte with terrible injuries including severe brain damage but she was still able to identify her attacker to police.

Detectives noticed the similarities between the two attacks and arrested Celaire after using a change in the double jeopardy law to reopen the Cassandra McDermott case.

Under the old law, anyone acquitted by a jury could not be retried even if new evidence was uncovered. But in 2005 the 800-year-old legal principle was repealed in England and Wales, allowing the court of appeal to order a retrial if the evidence was strong enough.

At the start of his second trial in May this year, the one-time Maidstone Town defender pleaded guilty to the manslaughter of McDermott and the attempted murder of Hoyte.

Celaire admitted he attacked McDermott after their four-year relationship ended. He slammed her head three or four times against a hard edge, such as a door, and then left her unconscious under a duvet in her room where she choked on her vomit and died.

He admitted to attacking Hoyte after the pair split up in 2007. Celaire, who changed his surname to McNish after his original murder acquittal, was sentenced at the Old Bailey to life in jail with a minimum term of 23 years.

Simon Denison QC, for the prosecution, told the court that Celaire had a history of violence towards women.

He was 15 when he took part in the gang rape of a vulnerable 17-year-old girl at Lewisham College. He and the attackers lured the girl into a basement.correct a spCelaire contested the allegation but was found guilty and jailed for five years, reduced on appeal to four years.

Cassandra McDermott was 15 and Celaire 19 when they began a volatile relationship in 1997. Police were called numerous times to deal with violent disturbances but McDermott repeatedly refused to press charges.

One night on October 2001 – three weeks before McDermott's 20th birthday – Celaire launched the fatal attack.

"This was a sudden violent assault in which Cassandra suffered four or five hard blows to the face that left her unconscious on the bedroom floor," said Denison.

"The cause of her death however was tragic. While she was lying on her back unconscious, she vomited. Being unconscious, she was unable to clear her airways and inhaled the gastric contents into her lungs and died."

The crown had to accept Celaire's plea of manslaughter as there was no evidence of a sustained assault or the use of a weapon, Denison said.

Six years after killing McDermott, Celaire took a hammer to Hoyte's head after she began a relationship with another man.

Hoyte was found lying in her bedroom covered in blood having suffered severe injuries.

The court heard that Celaire "callously" visited her in hospital days after the attack thinking that she would never be able to tell her story. Her mother, Eunice Lander, was with her and encouraged him to hold her hand but she pushed him away and put her hand over her face.

Later Hoyte identified Celaire as her attacker when her mother wrote a series of names on a board and she pointed and banged at the word "Mario".

It was some time before she was able to speak to police who painstakingly built up an account of what had happened. She told officers that Celaire had confessed to her about killing McDermott.

Hoyte described how on the night of the attack she had thought Celaire was leaving her flat and said "bye bye" to him.

"She was then hit on the left side of her head. 'Bang, bang, bang,' she said, then she was lying on her bed. She described blood dripping on to the floor," Denison told the court.

Mrs McDermott, 58, said in a victim impact statement read to the Old Bailey today: "My heart goes out to Kara for her bravery and determination.

"She has shown immense courage to see this process through of telling her story but also of the confession that Mario made to her of killing Cassandra.

"It was Kara's determination for justice that made it possible for Cassandra's case to be reopened."

There was loud applause and a shout of "rot in hell" in court as Celaire was jailed.

The judge, Paul Worsley, told the defendant: "You present a very real and continuing danger to young women with whom you enter into a close relationship."

Celaire was given two life sentences and told he must serve a minimum of eight years after pleading guilty to the manslaughter of McDermott. He was given a concurrent life term with at least 23 years for the attempted murder of Hoyte.

In a letter read out in court, Hoyte told her attacker that she was determined to rebuild her life.

"Mario, why did you do this to me?" she wrote.

"I don't hate you, I pity you. I will get better and better with each day and stronger. You have only damaged my shell, I am still the same determined and strong person I always was … I leave here today free, with the whole world at my feet and a new life to be whatever I choose to be.

"You, on the other hand, have a long time to reflect and to understand you cannot control another person – that their life is just that: theirs."